The present invention relates to a power saving control function for a computer such as a personal computer.
Various portable notebook type personal computers capable of operating by batteries have recently been developed. A computer of this type has various power saving functions in order to prolong the continuous operation time of the system by a battery as long as possible. One of them is a power saving function concerning a display device such as an LCD or CRT.
Standards for the power saving function include the International Energy Star standard which defines that a computer must comprise a function capable of activating the low-power mode and deep sleep mode of a display. The low-power mode is the first low-power state which is automatically activated after the computer does not operate for the first predetermined time. The deep sleep mode is the second low-power state which is automatically activated when the computer does not operate for the second predetermined time. According to this standard, the shift time for activating the low-power mode must be set within 30 min, and the shift time must be set to activate the deep sleep mode within 70 min. Furthers the total of the shift times to the low-power mode and deep sleep mode must fall within 70 min. Note that the shift time is changeable by the user.
For example, if the computer does not operate for a predetermined time or more set by the user, an operating system (to be simply referred to as an OS hereinafter) generates the first operation mode signal for shifting to a standby state (corresponding to the low-power mode) in which the screen display is turned off. Further, if the computer does not operate for another predetermined time or more set by the user, the OS outputs the second operation mode signal for shifting to a power-off state (corresponding to the deep sleep mode). The BIOS receives these mode signals, and controls the display controller to control the operation state of the display.
In this manner, if a non-operation state continues for a certain time or more, power consumption is temporarily reduced, and then the display is turned off. In other words, a plurality of stages (two stages in this example) of the power saving state are set. If a mouse or keyboard is operated in either the standby state or power-off state, display resumes. In a CRT, the time until display resumes is shorter in return from the standby state than in return from the power-off state. For this reason, when the computer with the CRT does not operate for a predetermined time, it is not immediately set to the power-off state but temporarily to the standby state.
Some other OSs further divide the standby state into a plurality of states, and gradually reduce power consumption through a plurality of states.
In general, a so-called server OS having an advanced network-compatible function does not take multistage power saving control, and directly shifts to the power-off state after the non-operation state continues for a predetermined time, i.e., takes only two, power-on and power-off states.
Most of the OSs of conventional computer systems first output a standby mode signal when a computer does not operate for a predetermined time, and then output a deep sleep mode signal to set the power-off state when the computer does not operate for another predetermined time.
However, some users attach importance to the power saving effect more than the time-shortening effect until display resumes, do not require the multistage power saving state, do not desire to set the power-off state after the standby state is temporarily set, but desire to directly set the power-off state. When an LCD is used in place of a CRT, the time until display resumes is almost the same between return from the power-off state and return from the standby state.
In this manner, most of conventional OSs cannot cope with a demand for directly setting the power-off state when the computer does not operate for a predetermined time, in order to enhance the power saving effect.
Along with upgrading (function advance) of an OS, the upgraded version of the above-mentioned OS (if the non-operation state continues for a predetermined time, the OS first outputs a low-power mode signal, and if the non-operation state further continues, outputs a deep sleep mode signal) can be used as a server OS. When the server OS, which immediately shifts to the power-off state in non-operation, is upgraded, the display device of a client is not immediately set to the power-off state but is temporarily set to the standby state. A client user who does not know the change of the OS or forgets it may mistake this state for a malfunction of the computer, and may be confused. Even a user who knows the change of the OS may feel unnatural if display operation changes.